Apparatus for the treatment of plastic materials



July 20, 1965 J. CARTON ETAL 3,195,178

APPARATUS FOR THE TREATMENT OF PLASTId MATERIALS Filed Aug. 1. 1961 3Sheets-Sheet 1 Fi I Fig.2

9- Pi 9.4 R 95 lgvenlors y 5 J. CARTON ETALQ 3,195,173

APPARATUS FOR THE TREATMENT OF PLASTIC MATERIALS Filed Aug. 1, 1961 5Sheets-Sheet 5 A Home yg.

United States Patent 3,195,178 APPARATUS FUR THE TREATMENT OF PLASTICMATERIALS Jean (Iarton, Paris, and Jean Feytis and Pierre Fouquet,

Bohain (Aisne), France, assignors to Compagnie FrancaiseThomson-Houston, Paris, France Filed Aug. 1, 1961, Ser. No. 128,465Claims priority, application France, Aug. 10, E60, 835,527 9 Claims.(Cl. 18-2) The present invention relates to an apparatus for processingplastic materials which are under the conditions of production purelyviscous or visco-elastic; and also to a type of machine suitable forprocessing the said materials.

It is known that the mixtures based on elastomers or on thermoplastic orthermosettable synthetic resins prepared in mixers of different typeswhich are well known in the rubber and plastic-materials industry maypresent occlusions of air, traces of moisture and/or components whichare volatile under certain conditions of temperature and/ or ofpressure.

The thermal treatments necessary for putting these mixtures into theirfinal form (for example, vulcaniza tion), even when carried out withconcomitant application of a certain pressure (realized either withsteam or by molding in a press) impart to the obtained products a moreor less spongy structure. The proof of this is that the theoreticaldensity, calculated on the basis of the density of each of thecomponents, is never attained in practice.

It is an object of this invention to provide products whose density willbe as close as possible to the theoretical density. Another object is toapply to the mixtures suitable thermal treatments (such asvulcanization) without application of any pressure, thereby contributinga worthwhile simplification in comparison with the previous techniques.

In brief, the invention provides an apparatus which enables separationand removal from plastic materials of all gases and components which arevolatile under the conditions of processing. It is thus possible to ridthe viscous or visco-elastic materials of the gases or volatileinclusions which usually impart a heterogeneous structure to thefinished products produced from the said materials.

This method and apparatus for carrying it out are based on the discoveryby the applicant of the facts which will hereinafter be described andresulting from the combination under rarefied atmosphere of a thermalaction and a mechanical action.

An object of the invention is to provide plastic material degassingapparatus which is new, simple, cheap and robust.

A further object of the invention is to provide apparatus for thecontinuous processing of plastics including the application of degassingthereto.

The term plastic materials as used herein and in the claims is to bedeemed as including any viscous polymeric compositions, includingresins, elastomers, ceramic pastes and the like.

In order that the invention and its advantages may be more fullyunderstood, there will now be described, by way of example and withreference to the accompanying drawings, some embodiments of the improveddegassing apparatus, it being understood that these examples do not haveany limiting character with respect to the mode of carrying out theinvention or to the applications to which it may be put, especiallythose concerning the treatment of ceramic pastes.

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In the drawings:

FIGURES 1 to 5 illustrate the principle of the invention;

FIGURE 6 is an elevational section of one embodiment of apparatus;

FIGURES 7, 8 and 9 are alternative cross-sections for the apparatus ofFIGURE 6, all taken on line 7"i of FIGURE 6;

FIGURE 10 is an elevational section of another embodiment;

FIGURES ll, 12 and 13 are alternative cross-sections for the apparatusof FIGURE 10, all taken on the line I2-12 of FIGURE 10;

FIGURE 14 is an elevational section of a further embodiment;

FIGURE 15 is a cross-section of the embodiment of FIGURE 14 on line15-l5 of FIGURE 14;

FIGURE 16 is an elevational section of yet another embodiment;

FIGURE 17 is a cross-section of FIGURE 16 on line 1717 thereof;

FIGURE 18 is an elevational section of a further embodiment;

FIGURE 19 is a cross-section of FIGURE 18 on line 19-19 thereof, and

FIGURES 20 to 23 are views of yet another embodiment; FIGURES 20 and 21being cross-sections taken on line 2)-20 of FIGURE 21 and on line 21-21of FIG- URE 20 respectively.

In FIGURE 1 there is shown in hatching a bead 163 of plastic materialpressed between a plane surface 1% and a so-called scraper surface 101,travelling across the surface 1th), the scraper surface being limited bya straight line 102 in the plane 100.

The scraper surface 101 is moved relatively to the plane surface 10!) inthe manner of a scraper or putty knife blade. This movement produces awedg-ing or squeezing of the bead 103, along the straight line 162.

According to a preferred aspect of the invention the coefiicient offriction of the material with respect to the scraper surface 101, mustbe smaller than the coefficient of friction of the material with respectto the plane surface 100. By reason of these arrangements, there isproduced a rolling and kneading movement in the bead, whereby eachelementary volume thereof is subjected in succesion to (a) adisplacement until it reaches the free surface 103 of the bead; and (b)at the free surface, a stretching of the material which bursts thebubbles and occluded gases and vapors present in the material.

For illustrating this action there are shown in FIGURES 2, 3, 4 and 5,the successive positions with passage of time of an elementary volumeinitially located at 104a in the interior of the bead. This volumeencloses a bubble of gas or a component which becomes volatile under theaction of heat and/or vacuum. This bubble passes through the positions104b, 184a and finally reaches the free surface of the bead at 104dwhere it bursts.

For obtaining equivalent results it is clear that the planar surfacesand lttl may be replaced with other surfaces, provided that thefollowing three conditions are fulfilled:

Condition A The material, in the form of a viscous or visco-elastic beadmust be squeezed between two active surfaces in relative movement andmaintaining a line of angular contact in such a way that the materialundergoes a decreasing wedging action from the line of angular contactof the surfaces to the free surface of the head. In other words, a steepnegative pressure gradient must be present as from the innermostportions of the bead adjacent the line of contact, where a high pressureobtains, to the free Condition B During movement, the bead must alwayspresent to the, subatmospheric atmosphere a free surface and hencewithout contact with the solid parts of the machine.

Condition C The so-called scraper surface draws the bead along with itand it is essential that the coefficient of friction of the materialagainst the scraper surface be smaller than the coefficient of frictionof material against the other or base surface. This differential betweenthe coefficients of friction may be obtained through one or more of thefollowing means:

(1) Different materials;

(2) Different surface conditions;

(3) Different surface temperatures.

Some embodiments satisfying conditions A, B and C are shown in FIGURES 6to 9. FIGURE 6 represents the longitudinal section common to the threeembodiments shown in cross-section in FIGURES 7, 8 and 9. These latterfigures show the section of the plane scraper surface and the othercylindrical active surface executing a relative movement under rarefiedatmosphere. There may be a clearance of the order of, for example, mm.between the surfaces.

In FIGURES 6 and 7 there is seen a recessed cylindrical body 105, withinwhich is rotatably mounted, by suitable means not represented, aprismatic body 1116 providing the scraper surfaces. The body 105 is incommunication via an opening 146 with a vacuum pump. A clearance space147 is provided between the inner body 106 and an end closure member 107closing the body 105 at one of its ends.

The body'defining the scraper surfaces, pressing the bead 108, may beformed of other polygonal shapes as shown at 106a and 1116b in FIGURES 8and 9 respectively.

The arrangements for controlling the pressure and/ or the temperature,as well as the corresponding actuating means, are not shown. These maycomprise the usual arrangements well-known for use with thesetechniques, such as electric resistances, fluid circulating coils, fins,etc.

The location of the vacuum connection is not critical. It may be locatedat any place not covered by the bead of material. Another aspect of theinvention resides in the possibility of incorporating it in a continuousproduction process. For this purpose the arrangements according to thepresent invention must satisfy conditions A, B and C as set forth above,and, in addition, a condition D as set forth below.

Condition D The performance of a continuous process requires theexistence in the apparatus of three successive sections. Namely:

(a) A feeding section serving to supply to the following section thematerial in viscous or visco-elastic phase at a prescribed rate ofdelivery and at a prescribed temperature.

(b) A special processing section for the extraction and entrainment ofthe volatile components, according to the present invention, satisfyingtogether conditions A, B and C and. that of replenishment of thematerial.

(c) An output section. which receives the product of the processingsection and delivers it to the intended utilization apparatus.

Sections (a) and (0) may consist of any known arrangement such as usedin presses, molders, etc. Thus,

- gravity feed means, auger screw feeders, and the like, may

be used. Auger screws are particularly convenient and hence preferred. 7

Thus, any of the arrangements of FIGURES 6 to 9 can satisfy condition Dabove if it maintains a vacuum and if it is provided with two orificesrespectively connectable with a feedingand an. outlet-section and thematerial is replenished either by gravity or by pressure or by any otherequivalent effect. i

This aspect of the invention is illustrated by several nonlimitingembodiments shown in FIGURES 10 to 23.

The various arrangements for measuring and regulating the temperaturesand/ or vacuums are not shown on these figures, since these mayconstitute known arrangements customarily employed in relatedtechniques.

Eachof the five embodiments to be described comprises a similar feedingsection and a similar output section. The feeding section comprises ineach case a feed screw or anger 114 fed conventionally through anopening 113 in the body 112. This screw is rotatable relatively to thebody 112. Such a section terminates in a delivery-limiting portion whichcan be realized by any known arrangement, for example, it can take theform of an annular constriction between the body 112 and an enlargement115 of the shank of the screw.

The output section 111 comprises in each of the five embodiments aconventional auger or feed screw 116 rotatable in the body 112. Itevacuates the treated material from section 111D and extrudes it througha conventional extrusion head (not shown). This section is filled withthe material which is recompressed therein.

There is shown in FIGURE 10 the elevational section of a type of feederwhich comprises a screw whose portion located in section 110 has aspecial thread 118, described below. Processing section 110 forextracting the gaseous bodies is in communication with the vacuum pumpthrough an opening 117 in the body 112. The scraper surfaces driving thebeads of material are helicoidal, and the cross section of one of thesescraper surfaces is the straight segment 119-1211, as shown in FIGURE 11or 12 or 13. Accordingly any polygon can constitute the cross section ofthe processing section of such a screw provided the wedging angle issuitable for the material to be treated. The other or base surface isconstituted by the cylinder of revolution which limits the body of thefeeder internally.

Conditions A and B are fulfilled only if the bead does not extend intothe region of the straight segment 119421 defining the cross section ofeach helicoidal surface. For this purpose the delivery rate of thefeeding section is adjusted to a value low enough to ensure that thebead of material will not completely 'fill the channels in theprocessing section, but will leave a free surface to the bead.

Condition Ciis realized, for example, by chroming the screw surfaces toreduce the friction coeflicient between it and the processed material.The employment of a helicoidal scraper surface ensures the feed andreplenishment of the material in section 110. Thus condition D is fullysatisfied.

A preferred variation of the apparatus is shown in FIGURES 14 and 15.The general arrangement is the same as in FIG. 10. The cross-section ofthe screw in processing section 110 is shown in FIGUREIS.

The scraper surface driving each of the beads again is a helicoidalsurface whose cross section is a straight seg ment 124-125. In this casethere are provided four of these surfaces disposed swastika-fashion asshown in FIGURE 15. With each of these surfaces there is associated forlimiting the volume offered to'the head a helicoidal portion having astraight cross section 125-126 cutting the helicoidal scraper surface ata right angle.

Another embodiment of the apparatus is shown in FIGURES 16 and 17. Thegeneral arrangement is the same as in FIGS. 1015. The scraper surfacedriving each of the beads of material is a helicoidal surface whosecross section is for facilitating machining operations, a po1)ti-on129430 of an Archimedean spiral (FIGURE 17 The screw has two of thesescraper surfaces (which are displaced 180 deg.). The other or basesurf-ace is constituted by the cylinder of revolution which limits thebody of the feeder internally.

Another modification is shown in FIGURE-S 18 and 19. The generalarrangement again is similar to that of the foregoing embodiments.

The processing section comprises a rotatable cylindrical part 132,connected with the feed screw 114 and a stationary enclosure part 133.The scraper surface, here stationary, is a regular helicoidal surface134 whose cross section is, for facilitating machining operations, aportion 135-136 of Archimedean spiral (FIGURE 19). The other or basesurface is the rotatable cylindrical surface 132. The pitch of the helixis reverse from the screw pitches of the two other sections 1&9 and 111.Each scraper surface is formed on a flange having, for example, the form135, 136, 137 and 138 visible in FIG- URE 19. One or more such flangesmay be secured to the body 133 of the feeder, either by welding, asindicated in the figures, or by any other means, such as bolting,riveting, etc. The processing section is in communication with a vacuumpump through one or more openings 139 in the body of the feeder. Thearrangement shown in FIGURE 19 avoids presentation of the bead ofmaterial between the vacuum connections and thus wholly eliminates thedanger of the material being drawn out therethrough.

Conditions A and B are satisfied to the extent that the delivery rate ofthe feeding section produces a bead which is practically limited to theportion 135-136 of the helicoidal surface. Under these conditions thebead presents a free surface to the vacuum.

Yet another embodiment of the invention is shown in FIGURES 20 to 23.

The processing section comprises a frusto conical rotor 141 connectedwith the feed screw 114 and a stationary enclosure part 142 (FIGURE 21)connected with the body 112. To this stationary part 142 are connectedshoes 343, each of which presents to the truncated cone 141 a scrapersurface constituted, for example, by a portion of a conical surface, ofthe .same apex as the truncated cone 141, whose base is, for example, aspiral portion in the plane of the large base of the truncated cone(FIGURE 21). The base surface which cooperates with the scraper surfaceis the rotatable truncated cone 141, with which it is in contact along ageneratrix. This surface may alternatively be a cylindrical surface withgeneratrices parallel with the generatrix of contact or any othersurf-ace (as shown in FIGURE 22), adapted for fulfilling condition A.The feeding section has its delivery rate regulated in such a way thatthe bead always satisfies conditions A and B.

FIGURE 23 shows schematically the action on the head of arrangements ofthis type.

Condition D is realized when the material is introduced from the smallbase of the truncated cone.

The vacuum is connected at one or several points 149 of the body of thefeeder outside of the path of movement of the beads of material. Thisarrangement presents the important advantage of avoiding pressing of thematerial out through the vacuum connection.

In all of the embodiments described and shown, the teaching of theinvention regarding the difierential friction coefiicients between thetwo surfaces and the material being processed (condition C as definedhereinabove) may be fulfilled in any of various ways. For imparting thelower frictional characteristic to the scraper surface, said surface maybe chrome-plated (as mentioned in respect to certain of the embodiments)or it may be made of a suitable grade of metal having a substantiallysmoother surface condition than the cooperating surface.

The apparatus of the screw type shown in the drawings may havedimensions similar to those of conventional feeders of the same screwdiameter. The addition of the special processing section according tothis invention does not lower the output compared with the conventionalfeeders of the same screw diameter.

Although the five latter described embodiments have feedingandoutput-section arrangements of the auger type, it is to be understoodthat within the scope of the present invention then. could also beemployed presses or any other arrangement suitable for continuousproduction.

We claim:

1. Apparatus for processing plastic materials, comprising a sealedenclosure, and means defining an input section, a processing section andan output section in series relation lengthwise of the enclosure; meansdefining relatively movable surfaces in said processing section inmutual engagement along a line of angular contact to define generallylongitudinal channel means of uniform angularity in cross sectionthrough the processing section. One of said surfaces defining acontinuous backing surface and the other a vaned scraper surface; saidscraper sur face having a substantially lower friction coefficient thansaid backing surface with respect to said material; an opening in saidprocessing section communicating with said channel means and meansconnecting the opening with a reduced pressure source; means for feedingmaterial to said input section through said processing section and forwithdrawing processed material from said output section at relativerates so predetermined that the material does not completely fill theprocessing section; and means for continuously imparting relativemovement to said surfaces during material feed; whereby said materialwill be subjected in said processing section to a steep negativepressure gradient and an accompanying rolling and kneading action due todifferential friction against said surfaces for positively expellinggaseous inclusions from said material as they are presented to saidvacuum.

2. Apparatus as claimed in claim 1, wherein said opening is formed in anarea of said surfaces not accessible to said material during feedthereof through the processing section.

3. Apparatus for processing plastic materials, comprising a tubularstator member; an elongated rot-or member extending through androtatable in said stator memher and defining an input section, aprocessing section and an output section lengthwise of the statormember; there being generally continuous backing surface means on one ofsaid members in said processing section and vaned scraper surface meanson the other member engageable with said backing surface means along aline of angular contact to define generally longitudinal channel meansof uniform angular-ity through the processing section; said scrapermeans having a substantially lower friction coefficient means than saidbacking surface means with reference to said material; an opening insaid surface means communicating with said channel means and meansconnecting the opening with vacuum source; and means for feedingmaterial to said input section and for withdrawing processed materialfrom said output section at a rate so low as to incompletely fill saidchannel means; whereby the material will be subjected in said processingsection to a steep negative pressure gradient and an accompanyingrolling and kneading action due to differential friction against saidbacking and scraper surface means for positively expelling gaseous andvolatile inclusions from said material as they are presented to saidvacuum.

4. Apparatus as claimed in claim 3, wherein said backing surface meanscomprises a surface of revolution selected from within the groupconsisting of cylindrical and frusto-conical surfaces, and said scrapersurface means comprise helicoidal vaned surface means having edge portions engaging said surface of revolution under a constant angle lessthan 5. Apparatus as claimed in claim 4, wherein said helicoidal scrapersurface means has a polygonal cross sectional configuration.

6. Apparatus as claimed in claim 4, wherein said helicoidal scrapersurface means has a cross sectional eonfiguration in the general form ofa square having its sides extended in one direction to provide fourextension arms in a generally swastika-like configuration, and saidrotor member is rotated in a direction to advance said extension arms intrailing relationship.

7. Apparatus for simultaneously milling and degassing a plastic materialcomprising a stator structur and a rotor structure having cooperatingsurfaces defining a working space therebetween; said surface of one ofthe structures being a surface of revolution selected from within thegroup consisting of cylindrical and frustoconical surfaces and saidsurface of the other structure being a helicoidal surface meeting withthe first surface under a finite, constant angle less than 90 throughoutthe longitudinal extent of said workin-g space; the second surfacehaving a substantially lower friction coefficien t with respect to saidmaterial than the friction coeflicient of thefi-rst surface; meansconnecting said working space with a source of vacuum; means for feedingmaterial into said working space at a rate so low that said space isincompletely filled therewith; and means for rotating the rotorstructure in a direction to advance the material through said space byrolling and kneading the material between said surfaces due to saidfriction coeificient relationship and so as to present continuallyrenewed portions of material to said vacuum.

8. Apparatus for simultaneously milling and degassing a plastic materialcomprising a stator having a generally cylindrical inner surf-ace and arotor having a helicoidally vaned outer surface defining a working spacewith said stator surface; said rotor surf-ace meeting with said statorsurface under a finite, constant angle throughout the longitudinalextent of the working space; the rotor surface having a substantiallylower friction coefficient with respect to the material than thefriction coefficient of the stator surface; means connecting saidworking space with a source of vacuum; means for feeding material intosaid working space at a rate so low that said space is incompletelyfilled therewith; and means for rotating the rotor in a direction toadvance the material through said space while rolling and kneading itbetween said surfaces due to said'friction coefiicient relationship andso as to present continually renewed portions of material to saidvacuum.

9. Apparatus for simultaneously milling and degassing a plastic materialcomprising a rotor having a generally cylindrical outer surface and astator having a helicoidally vaned inner surface defining a workingspace with said rotor surface; said stator surface meeting with saidrotor surface under a finite, constant angle throughout the longitudinalextent of the working space; the stator surface having a substantiallylower friction coefiicient with respect to the material than thefriction coeiiicient of the rotor surface; means connecting the workingspace with a source of vacuum; means'for feeding material into theworking space at a rate so low that said space is incompletely filledtherewith; and means for rotating the rotor in a direction to advancethe material through said space while rolling and kneading it betweensaid surfaces due to said friction coefiicient relationship and so as topresent continually renewed portions of material to said vacuum.

References Cited by the Examiner UNITED STATES PATENTS 1,138,410 5/15Pointon 18-2 1,283,947 11/18 Steinle 18-12 1,836,355 12/31 Banbury 18-21,936,248 11/33 Lash et'al 18-2 2,368,102 1/45 Bowman 18-2 2,438,2813/48 Gordon 18-48 2,519,014 8/50 Bankey 18-2 2,694,224 11/54 Rhodes 1822,698,962 1/55 Swallow 182 2,702,410 2/55 Brown 18-48 2,744,287 5/56Parshall et al 18-12 2,765,490 10/56 Zona 18-12 2,803,039 12/57 Marshall182 2,817,876 12/59 Gandellli et a1. 18-12 2,894,280 7/59 Juve 18-22,977,098 3/61 Watson 18-2 XR WILLIAM J. STEPHENSON, Primary Examiner.

1. APPARATUS FOR PROCESSING PLASTIC MATERIALS, COMPRISING A SEALEDENCLOSURE, AND MEANS DEFINING AN INPUT SECTION, A PROCESSING SECTION ANDAN OUTPUT SECTION IN SERIES RELATION LENGTHWISE OF THE ENCLOSURE; MEANSDEFINING RELATIVELY MOVABLE SURFACES IN SAID PROCESSING SECTION INMUTUAL ENGAGEMENT ALONG A LINE OF ANGULAR CONTACT TO DEFINE GENERALLYLONGITUDINAL CHANNEL MEANS OF UNIFORM ANGULARITY IN CROSS SECTIONTHROUGH THE PROCESSING SECTION. ONE OF SAID SURFACES DEFINING ACONTINUOUS BACKING SURFACE AND THE OTHER A VANED SCRAPER SURFACE; SAIDSCRAPER SURFACE HAVING A SUBSTANTIALLY LOWER FRICTION COEFFICIENT THANSAID BACKING SURFACE WITH RESPECT TO SAID MATERIAL; AN OPENING IN SAIDPROCESSING SECTION COMMUNICATING WITH SAID CHANNEL MEANS AND MEANSCONNECTING THE OPENING WITH A REDUCED PRESSURED SOURCE; MEANS FORFEEDING MATERIAL TO SAID INPUT SECTION THROUGH SAID PROCESSING SECTIONAND FOR WITHDRAWING PROCESSED MATERIAL FROM SAID OUTPUT SECTION ATRELATIVE RATES SO PREDETERMINED THAT THE MATERIAL DOES NOT COMPLETELYFILL THE PROCESSING SECTION; AND MEANS FOR CONTINUOUSLY IMPARTINGRELATIVE MOVEMENT AND SAID SURFACES DURING MATERIAL FEED; WHEREBY SAIDMATERIAL WILL BE SUBJECTED IN SAID PROCESSING SECTION TO A STEEPNEGATIVE PRESSURE GRADIENT AND AN ACCOMPANYING ROLLING AND KNEADINGACTION DUE TO DIFFERENTIAL FRICTION AGAINST SAID SURFACES FOR POSITIVELYEXPELLING GASEOUS INCLUSIONS FROM SAID MATERIAL AS THEY ARE PRESENTED TOSAID VACCUM.